Bumping the version of phoenix to 1.7 and Phoenix_html to 4.1

[Santhosh-KS]

Build is failing for the
Phoenix- 1.8.rc3 candidiate
Updated the versions to Phoenix and Phoenix_html to 4.1

Here is the original error message

 mix deps.get
Resolving Hex dependencies...
Resolution completed in 0.079s
Because every version of phoenix_pages depends on phoenix_html ~> 3.3 and your app depends on phoenix_html ~> 4.1, no version of phoenix_pages is allowed.
So, because your app depends on phoenix_pages ~> 0.1, version solving failed.
** (Mix) Hex dependency resolution failed